1. Field of the Invention
This invention relates to a package for coupling an optical fiber and an optical device and an optical fiber-optical device module, and more particularly to a package for coupling an optical fiber and a light emitting element or an optical fiber and a photodetector and an optical fiber-optical device module accommodated in and integrated with such package.
2. Description of the Related Art
A module including an optical fiber and an optical device converts an electric signal in transmission into an optical signal or converts an optical signal into an electric signal.
Modules of the type mentioned allow transmission of parallel signals between different electronic systems or between different circuit boards in an electronic system, and accordingly, the characteristics of electronic system are improved in terms of noise, crosstalk or transmission rate.
Where signals are transmitted between a plurality of electronic computers or signals are transmitted between different circuit boards in an electronic computer, the rate of signal processing in such electronic computer or computers can be raised by converting an optical signal into an electric signal and converting an electric signal into an optical signal.
In order to couple an optical fiber and an optical device to each other, it is required to develop a package of a small size with which such coupling can be performed readily. In this instance, a package for an optoelectronic coupling module is used to couple an optical fiber and optical devices such as a semiconductor laser or a light emitting diode or to couple an optical fiber and a light detecting element such as a PIN-photodiode. It is to be noted that a light emitting element, a photodetector, an optical waveguide modulator and other like elements are generally referred to each as an optical device herein.
A package having such a structure as shown, for example, in FIGS. 1(a) and 1(b) has been proposed as a package of the type described above. The package is disclosed in [1] T. Karo et al., IEEE Proc. 42nd Electronic Components and Technology Conference pp. 853-860, 1992.
Referring to FIGS. 1(a) and 1(b), a photodiode 101 serving as a light detecting element is placed on the bottom of a package body 100 which is open at the top thereof, and a optical fiber 102 extends through a side wall of the package body 100 and the extreme end of the optical fiber 102 faces to a light receiving portion of the photodiode 101. The package body 100 is closed at the top thereof with a lid 103. The photodiode 101 and the optical fiber 102 are fixed in an opposing relationship to each other on a support table 104. Upon positioning, one of the photodiode 101 and the optical fiber 102 is fixed, and in this condition, the other is positioned relative to the one using a jig.
With the package of the structure described above, in addition to a space required to mount the photodiode 101 and the optical fiber 102, spaces S for accepting such jig must be assured, which makes an obstacle to minimization of the package.
Besides, since the photodiode 101 and the optical fiber 102 are supported only from the bottom of the package, in such a condition that a plurality of such combinations are arranged in parallel to each other as shown FIG. 1(a), then torsion is likely caused between the photodiodes 101 and the optical fibers 102 by deformation of the bottom of the package or the support table 104 arising from thermal expansion so that optical axes of the photodiodes 101 and the optical fibers 102 are put out of alignment with each other. Such disalignment is remarkable where a multi-channel optical device and multichannel optical fiber are coupled to each other.
It has been proposed in the following documents to attach an optical device to an end of an optical fiber array in order to prevent such disalignment as described above. However, neither of the documents discloses a structure of a package for accommodating them in an airtight condition. See, for example, [2] U.S. Pat. No. 4,730,198 and [3] Yusuke Ota, Robert G. Swartz, IEEE The Magazine of Lightwave Telecommunication Systems, Vol.2 , No. 2, pp. 24-32, May 1991
Another structure has been proposed and is shown in FIG. 2 wherein optical fibers 107 and optical devices 108 are coupled to each other and an electronic part 106 such as an LSI is accommodated in a package 105. The package 105 has a bottomed structure with the top opened, and a space which is required to mount the optical fibers 107 and the optical devices 108 is assured around the electronic part 106 and the optical devices 108. The module of the type just described is disclosed, for example, in [4] Japanese Patent Laid-Open Application No. Sho. 63-18308.